HAMPSTEAD, N.H. – Matt Mowers touts he’s "the only one" in a crowded field of Republican candidates who can defeat two-term Democratic Rep. Chris Pappas in November’s midterm elections in New Hampshire’s First Congressional District, which has long been a highly contested swing House district. 

As he runs for re-election, Republicans view Pappas as vulnerable amid a political climate that for the past year had favored the GOP. Republicans need a net gain of just five seats in the 435-member House in November’s midterms to take back the chamber’s majority they lost in the 2018 elections, and they’re heavily eyeing New Hampshire’s First District, which stretches from the Massachusetts border, Manchester, and the Seacoast region, up through the Lakes region and into the White Mountains.

‘Everyone sees we need a tested conservative winner and that’s exactly what we are. It’s exactly what I’ll do. Every poll shows that I’ll beat Chris Pappas," Mowers told Fox News on Monday, on the eve of New Hampshire’s primary.

Mowers, a former New Hampshire GOP executive director who worked on former President Donald Trump's 2016 presidential campaign and served in the State Department during the Trump administration, easily captured the 2020 congressional nomination in the district before losing to Pappas by five points in the general election. 

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"This has always been about who is the tested America First fighter for New Hampshire, and I’ve always been the one who’s stepping up to say that I will," Mowers showcased. "I’m the only one who worked with President Trump to stop the influx of illegal drugs. I worked with President Trump to establish the Keystone XL pipeline and worked to get it approved. I worked with him to take on entrenched bureaucracy."

But the 33-year-old Mowers faces a fierce rival for the GOP nomination in 25-year-old Karoline Leavitt, who’s repeatedly targeted Mowers in a Republican primary that’s turned increasingly combustible.

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The most recent public opinion poll indicated Leavitt – a New Hampshire native who worked in Trump’s White House press shop and later for GOP Rep. Elise Stefanik of New York, who is now the number three ranking House Republican – is just two points behind Mowers in the race for their party’s nomination.

"I’m proud to be the home-grown America First candidate in this race," Leavitt, who would become the youngest woman ever elected to Congress if she wins the primary and again in November, told reporters on Thursday, as she campaigned in Londonderry, New Hampshire, with a very high-profile surrogate – conservative firebrand Sen. Ted Cruz of Texas.

"He already proved to us that he lost to Chris Pappas. He cannot win in this general election, Leavitt charged.

The battle between Leavitt and Mowers has been one to the right, with both showcasing their Trump administration experience. However, Mowers does not go as far as Leavitt when it comes to Trump’s 2020 election loss to President Biden. Leavitt is a firm supporter of the former president’s unproven claims that the last election was "rigged" with "massive voter fraud" and "stolen." Mowers, with more pragmatic language, has said that he continues to have concerns about voting "irregularities around the country."

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Trump, who endorsed Mowers two years ago, stayed neutral in this year's showdown.

Leavitt has attacked Mowers as "a career politician," and argued to Fox News that "Matt Mowers can’t answer a question to save his life because he is bought and paid for by the party bosses down in Washington, D.C. I am straightforward with voters. They know where I stand."

Mowers – who in June was endorsed by House Minority Leader Kevin McCarthy and Minority Whip Steve Scalise, who are the top two Republicans in the chamber – is being backed by a seven-figure ad buy from the Congressional Leadership Fund, a powerful super PAC aligned with the House GOP leaders. Additionally, another outside Republican group, the more moderate Defending Main Street Super PAC, has spent more than $1 million to blast Leavitt on the airwaves.

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Asked about the big bucks flooding into the district, Mowers said, "It tells me that folks know we’re the one who’s going to win this race and defeat Chris Pappas… this is the seat that is going to determine whether Nancy Pelosi is speaker of the House again."

But Leavitt emphasized that "the people are with me" and charged that "the establishment in Washington is viciously smearing me with $5 million in negative attack ads."

Democrats say the combative GOP primary will hurt Republican chances in the general election.

Pappas predicted on Saturday that "whoever the nominee is, they’re certainly going to be banged up by this process."

And Democratic Congressional Campaign Committee spokesperson James Singer claimed that "this GOP primary’s race to the right has fractured the party and weakened any Republican nominee in the general. Their MAGA Republican nominee will be unable to scrub the far-right, anti-abortion positions they have chosen to stake out."

The attacks and counterattacks involving Leavitt and Mowers and their allies may open the door to Gail Huff Brown, a former longtime TV news reporter and wife of former Republican Sen. Scott Brown, who served as U.S. ambassador to New Zealand during the Trump administration. The most recent poll – from the University of New Hampshire Survey Center – indicated Huff Brown in third place but gaining ground. The survey also indicated two other candidates in the GOP primary – former state senator and executive councilor Russell Prescott and state Rep. Tim Baxter – in single digits.

"I think the voters are tired of the negative and they’re tired of the negative advertising they see on TV. They’re tired of the money – millions of dollars pouring into New Hampshire," Huff Brown told Fox News on Monday in Derry, New Hampshire. "People are tired of all of that. And my hope is that people see right down the middle there is me. And I am somebody who has always been open, I’ve always been transparent."

Huff Brown, who touts her "skills and life experience," grabbed attention the past couple of weeks with a TV ad on the combustible issue of abortion, where she spotlighted her personal and emotional experience in a high-risk pregnancy and her support for "choice." 

"In Congress, I’ll vote to protect the New Hampshire law, and the choice it guarantees," Huff Brown says at the end of her spot. With Leavitt, Mowers and the rest of the GOP primary field taking a harder anti-abortion stance, Huff Brown may appeal to last-minute and less ideological Republican and independent voters.

Pointing to her rivals, Huff Brown stressed that "I believe I’m the only one who can beat Chris Pappas and I wouldn’t have gotten into this race otherwise."

The primary battle has grabbed the national spotlight, with plenty of attention in recent days from national publications

And Cruz is far from the only potential presidential contender to weigh in on the race in New Hampshire, which for a century’s held the first primary in the race for the White House. 

Former South Carolina Gov. Nikki Haley, who served as ambassador to United Nations during the first two years of the Trump administration, is backing Mowers and rallied with him in New Hampshire earlier this year. Additionally, Sen. Tom Cotton of Arkansas met with Mowers in New Hampshire last month. Mowers also enjoys the endorsement of former Secretary of State Mike Pompeo.

Meanwhile, major figures in the GOP who are allied with Trump – such as Stefanik, Rep. Jim Jordan of Ohio, and Sen. Mike Lee of Utah – are supporting Leavitt.